Rotation and shear control of a weakly magnetized plasma column using current injection by emissive electrodes

Abstract

The evolution of the radial profile of the rotation of a weakly magnetized plasma column is investigated experimentally in a radio-frequency argon plasma at low pressure when a strong electron current is emitted by large emissive cathodes. Current injection from large emissive cathodes over a background plasma column (with a plasma density of a few $10^{18}\ \textrm {m}^{-3}$ ) is characterized. Radial scans of the ion velocity show that a continuous control of the rotation profile may be obtained using two spatial configurations for the locations of the emissive cathodes (either in the centre or at the edge of the plasma column). The rotation profile results from the electric drift velocity, damped by the drag exerted on the ions. We demonstrate that the evolution of the rotation profile with the injected current is then controlled by the modification of the plasma potential profile in the presence of strongly emissive cathodes.

Nonlinear interactions of ion acoustic waves explored using fast imaging decompositions

“…This is well explained by a Doppler shift due to the plasma column rotation. The plasma column indeed rotates, as was reported previously 53 , where the electric drift E × B B 2 = −∇ r φ p /B e θ was shown to overcome the diamagnetic drift…”

“…The effective friction due to the ionization originates from ions created with a temperature much lower than the surrounding T i and depends upon the ionization frequency ν iz , computed as ν iz = n n K iz,0 T 0. with K iz,0 = 2.34 × 10 −14 m 3 /s and ε iz = 17.44 eV, and T e in eV 55 . A global damping factor K is then given 31,53 as…”

Velocity of plasma rotation in reflex discharge with themionic cathode

“…We will assume that the rotation speed at an infinite distance from the center is not infinite. Then, proceeding from (14), at infinity the velocity has the form u iϕ = 1/K d , where K d = 1 + 1/χ 2drag factor, which is consistent with the papers [22,23], in which this rotation speed was obtained by neglecting the convective derivative in the left side (5) compared to the terms in the right side.…”

Скорость Вращения Плазмы В Отражательном Разряде С Термокатодом

“…Будем считать, что скорость вращения на бесконечном расстоянии от центра не бесконечна. Тогда, исходя из (14), на бесконечности скорость имеет вид u iϕ = 1/K d , где K d = 1 + 1/χ 2 -коэффициент торможения (drag factor), что согласуется с работами [22,23], в которых данная скорость вращения получена при пренебрежении конвективной производной в левой части (5) по сравнению со слагаемыми в правой части.…”